Rear bumper for an automobile



FIG. 1 is a front and left side perspective view of a rear bumper for an automobile showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a left side view thereof; and,

FIG. 5 is a right side view thereof.

The broken lines in the drawings illustrate portions of the rear bumper for an automobile that form no part of the claimed design. 

CLAIM The ornamental design for a rear bumper for an automobile, as shown and described. 